[Co(NH3)4Cl(NO2)]Cl will show:
A. Solvate isomerism
B. Linkage isomerism
C. Coordination isomerism
D. Ionisation isomerism
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → B and D only
Structural isomers of coordination compounds differ in their bonds: linkage isomers need an ambidentate ligand; ionisation isomers exchange a ligand with the counter ion; coordination isomers need both cation and anion to be complexes; solvate isomers differ in whether water is a ligand or water of crystallisation.
(A) Solvate isomerism — Incorrect. The compound contains no water (solvent) molecule, so no solvate isomer is possible.
(B) Linkage isomerism — Correct. \( \ce{NO2^{-}} \) is ambidentate: it can bind through N (nitrito-N) or through O (nitrito-O, −ONO): \( \ce{[Co(NH3)4Cl(NO2)]Cl} \) and \( \ce{[Co(NH3)4Cl(ONO)]Cl} \).
(C) Coordination isomerism — Incorrect. This needs two complex ions (cationic and anionic) exchanging ligands; here the anion is a simple \( \ce{Cl^{-}} \).
(D) Ionisation isomerism — Correct. The counter ion \( \ce{Cl^{-}} \) can exchange places with the \( \ce{NO2^{-}} \) ligand: \( \ce{[Co(NH3)4Cl(NO2)]Cl} \) and \( \ce{[Co(NH3)4Cl2]NO2} \) give different ions in solution.
NCERT (2026-27 edition):
Linkage Isomerism – “Linkage isomerism arises in a coordination compound containing ambidentate ligand. A simple example is provided by complexes containing the thiocyanate ligand, NCS−, which may bind through the nitrogen to give M–NCS or through sulphur to give M–SCN.”
Ionisation Isomerism – “This form of isomerism arises when the counter ion in a complex salt is itself a potential ligand and can displace a ligand which can then become the counter ion. An example is provided by the ionisation isomers [Co(NH3)5(SO4)]Br and [Co(NH3)5Br]SO4.”